Telephone-transmitter.



No. 858.984. PATENTED} JULY 2, 1907. N. H. HOLLAND &- e. w. KAUSBR.

TELEPHONE TRANSMITTER. APPLICATION FILED JULY 28. 1906.

"UNITED STATES Parana OFFICE.

NEWMAN H. HOLLAND AND GEORGE W. KAUSER, OF CHICAGO, ILLINOIS, ASSIGNORS TO ERNEST H. STOLZ, OF CHICAGO, ILLINOIS.

TELEPHONE-TRANSMITTER.

Specification of Letters Patent.

Application filed July 28. 1906. Serial No. 328,211.

To all whom 2'1 may concern:

do it known that we, NEWMAN H. HOLLAND, a subject. of the King of Great Britain and Ireland, and (isomer. W. KAISER, a citizenoi the United States of America, both residents of Chicago, in the countyv of Cook and State of Illinois, have invented certain new and useful Improvements in Telephone-Transmitters, of which the following is a specification.

The main object of this invention is to provide an improved form of telephone transmitter having a sound collector capable of giving sensitive response to weak sounds and of intensifying sound vibrations which reach it.

The diaphragm as used in the ordinary transmitter .is so stiff that it requires considerable power to give it perceptible motion and it is therefore practically unaffected by sounds Whose vibrations are of small amplitude. If extremely sensitive diaphragms are placed in transmitters of the usual form, the microphone contact would offer sufticient resistance to the vibration of such sensitive diaphragm as to dampen it and cause it to vibrate with a node in the vicinity of the microphone contact. Such vibration would have little or no effect in transmitting the sound. The herein described invention overcomes this difficulty by providing a hollow member or bridge over which a sensitive diaphragm is stretched. The edges of the bridge span a considerable area of the diaphragm and leave the spanned portion free to vibrate as a whole. The vibration is then transmitted by the bridge to a diaphragm of the usual form which spans the other end of the bridge. The-delicate vibrations of the air acting upon the sensitive diaphragm have the same effect upon the microphone as would be had by vibra- Lions of much greater intensity if acting directly upon a diaphragm of the usual form.

Theobject of this invention is accomplished by the device shown in the accompanying drawing, in which:

" Figure 1 is an elevation showing the general arrangementof the parts of an aurophone provided with a transmitter constructed according to this invention. Fig. 2 is a section of the transmitter on the line 22 of Fig. 1. Fig. 3 is a rear view of the same with the cover removed. Fig. 4 is a detail partly broken away showing the arrangement of the stop which limits the separation of the electrodes of the microphone. I In the construction shown in the drawings, the transmitter 5 is mounted in a fixed position at one end of the battery 6. The receiver 7 is connected in series with the transmitter and battery in the usual manner.

The casing of the transmitter has a plurality of apertures 10 in its front face to permit the sound vibrations to readily enter the interior'of the casing. Inward of the openings 10 and spaced away from the front wall of the casing is a tightly stretched diaphragm 11. This is preferably of parchment or some other thin membrane whichis extremely sensitive to sound vibration. A second diaphragm 12 of comparatively rigid material, preferably carbon, is supported by the diaphragm 11 and separated therefrom by a ringshaped member or bridge 13. The bridge 13 and carbon transmitter 12 are secured in position by means of springs 14. The bridge 13 is of considerably less diameter than the support- 15 which secures the edges of the diaphragm 11 and in the form shown is arranged concentrically of the support 15.

The diaphragm 12 forms one of the electrodes of a microphone. The other electrode. 16 is cup-shaped and its edges are inclined toward the diaphragm 12 in an outward direction. The cavityof the electrode 16 is preferably filled with granules 17 of conducting material such as carbon. These are preferably spherical in form so that they will readily move and adapt themselves to the space between the electrodes. The electrode 16 is carried by a lever 18 which is mounted on a. spindle 19 having conical bearings in the adjustingscrew ZOand in the casing at 21. The lever l8'is eounter. weighted so'that the center ofgravity of the lever and electrode 16 is in the axis of the spindle 19. The electrode 16 and the parts connected therewith are comparatively heavy so that their inertia will provide considerable variation in the pressure upon the carbon granules during the vibration of the disk 12. The electrode 16 is normally urged against the diaphragm 12 by means of a spring 22 which is arranged to urge the electrode 16 to a normal position of close proximity to the diaphragm 12. Actual contact bet-ween the electrodes is however prevented by the presence ofthe carbon granules. The weight of the granules 17, on

account of the inclined walls of the electrode 16 tends to separate the electrodes of the microphone when the transmitter is in its normal upright position as when in use. The tension of the spring 22 is such as to slightly over-balance the tendency of the weight of the granules 17 toseparate the electrodes. An adjustable stop 23 is provided to preventthe electrodes from being jarred apart sufficiently to permit the granules 17 to fall out i of the pocket in the electrode 16. Y v The operation of the device shown is as follows: The sound waves vibrate the diaphragm 11 causing the por- 100. tion inclos ed by the bridge l3 to vibrate as a whole. This vibration is transmitted by the'bridge to the edges-of the diaphragm 1? which accordingly vibrates in barmony with the diaphragm 11. This is a molecular vibration and is transmitted in amanner exactly analogone to the transmission of the vibrations of a string to the sounding board of aviolin. The inertia of the electrode 16 resists the movement thereof sufficiently to cause considerable variation in the pressure of the granules 17 during the vibration of the diaphragm 12. T his. variation of pressure causes the changes in resistance in the electric circuit L of the microphone which modify the current so as to reproduce the sound at the receiver. I

What i claim as my inventionand desire to secure by Letters Patent is:

1. A transmitter comprising. a diaphragmsupported at its edges, a ringshaped member nearing loosely upon the diaphragm inward of its support and adapted to receive vibrations from. the diaphragm, a spring holdingsaid memher in position against said diaphragm and serving to stretch the portion of the diaphragm spanned by said n1e1nher, and a microphone operated by said member.

2. A transmitter comprising a diaphragm supported at its edges, a member bearing loosely upon said diaphragm inward of its support and spanning an area of the diaplrragm which is free to vibrate, a spring urging said-member against said diaphragm and serving to stretch the portion of the diaphragm spanned by said member, and a microphone receiving vibrations from said member.

3. A transmltter comprising a sensitive diaphragm secured at its edges, :1 ringshaped member bearing upon said diaphragm inward of its edges, :1 second diaphragm more rigid than the first spanning said member and adapted to receive vibrations from the first diaphragnrthrough said member, and a microphone receiving vibrations from said second diaphragm.

4. A transmitter comprising an annular support, a diaphragin spanning said support, an annular member having one end bearing on said diaphragm, said end being oi? less diametenthan said support and arranged concentrically thereof, a second diaphragm rigid as compared with the first and spanning the other end of said member, and a microphone arranged to receive vibrations from saidsecond diaphragm,

5. A transmitter comprising an annular support, a membranous diaphragm, such as parchment, stretched across eases said support, an annular member having one end resting on said diaphragm, said end being-of less diameter than said support and arranged concentrically thereof. an electrode comprising. a sheet of conducting material spanning the other end of said member, a spring urging said member against said diaphragm for stretching electrode coacting with said sheet edges for sheet.

6. A transmitter comprising an annular support. a sensitive diaphragm spanning said support, an annular memher having one end of less diameter than said support and bearing upon said diaphragm inward of said support, a comparatively rigid diaphragm spanning the other end of said member, a cup-shaped electrode located adjacent to said second d'iaphragn. a plurality of granules of conducting material supported by said cupshuped electrade in contact with said second diaphragm. and an electric circuit including said second diaphragm and cupshaped electrode and adapted to have varied through the vibration of said second diaphragm.

7. A transmitter comprising a diaphragm supported at its edges, a ring-shnped member having one-end 01 less diameter than said support and bearing upon said diaphragm inward of said support, a second diaphragm more rigid than the first spanning the other end of said nienr her, an electrode having a concave face adjacent to said second dia tllirae'm, a plurality of granules of conductin material supported by second diaphragm, the contour of said dissimilar to that of the adjacent end of said member, and an electric circuit including said second diaphragm and electrode and adapted to have the resistance thereof at a point inward of its transmitting sound through the vibration of said varied through the vibration of said second diaphragm Signed at Chicago this 26th day of NEWMAN n. noun-mo. GEORGE \V. KAL'SER. Witnesses E. A. ltmininmz, L. A. SMITH,

it. and a second the resistance thereof said electrode in contact with said.

concave face being 

